A papermaking apparatus is known which uses a finely-woven endless wire-screen and an endless felt-blanket belt provided in the sheet forming station of the papermaking apparatus. The wire-screen and felt-blanket belts provided in the sheet forming station of the papermaking apparatus are followed by a drying station and carry a wet web of paper toward the drying station during operation of the apparatus. The wire-screen and felt-blanket belts are thus subject to contamination with the wet web of paper being conveyed thereon and are for this reason provided with cleaning means to wash or rinse the belts while the belts are travelling with the wet web of paper carried thereon. Typical of such cleaning means are a vaned rotary felt whipper or beater, a felt conditioner and a shower pipe assembly as is well known in the art. The felt whipper or beat is provided with rotary vanes to beaten a felt-blanket belt to purge the dirt out of the blanket. The felt conditioner uses water ejection heads slidable on a guide bar extending in parallel with the direction of width of the felt-blanket belt and is adapted to spray hot water against the felt-blanket belt to clean the belt. On the other hand, the shower pipe assembly includes a hollow cylindrical water distribution pipe provided with a series of water ejection nozzles which project from the pipe and which are arranged at regular intervals in a longitudinal direction of the pipe. Water, hot or of normal temperature, or a mixture of water and a rinsing compound is directed under pressure into the water distribution pipe and is ejected from the individual water ejection nozzles onto the wire-screen or the felt-blanket belt during operation of the papermaking apparatus. The pipe thus arranged extends horizontally below the endless wire-screen or felt-blanket belt in the sheet forming station of the paper-making apparatus and is lengthwise movable in opposite directions parallel with the direction of width of the overlying belt.
A belt cleaner of each of these types, particularly a shower pipe unit, is driven to move back and forth below the wire-screen or felt-blanket belt by a drive unit which uses a cam and cam follower mechanism to dictate the reciprocating motions of the pipe. The use of such a cam and cam follower mechanism inevitably results in interruptions of the reciprocating motions of the pipe at the opposite ends of each stroke of the pipe. The repeated interruptions of the reciprocating motions of the water distribution pipe in turn result in localized cleaning of the wire-screen or felt-blanket belt, so that the belt may fail to be cleaned in some portions and may be cleaned excessively in other portions.
The water or the mixture of water and a rinsing compound used in an ordinary shower pipe unit is pressurized to 10 kgs/cm.sup.2 or less. Localized and accordingly excessive application of water streams onto the belt therefore tends to invite early wear of the belt and lessens the service life of the belt, particularly the felt-blanket belt. The use of a cam and cam follower mechanism in a known drive unit for a belt cleaner of a papermaking apparatus thus ultimately results in frequent exchanges of the wire-screen or felt-blanket belt and accordingly in considerable costs for the maintenance and servicing of the sheet forming station of the apparatus. Furthermore, an extremely large amount of water must be used to reduce the areas of the belt which may fail to be cleaned or which may be cleaned insufficiently. Consumption of such a large amount of water necessarily results in high costs for water and power.
Problems are further encountered by a known drive unit for a belt cleaner of a papermaking apparatus. These problems largely result from the increased production speeds of modernized papermaking machines which require belt cleaners to operate faster and at higher efficiencies. The cam and cam follower arrangement of known driving means for a belt cleaner is not capable of coping with such requirements, and is thus responsible for the disproportionately high costs for not only the maintenance and servicing of the sheet forming station but again for the consumption of power and water. These high costs are ultimately reflected by high market prices of paper and paper products.
It is, accordingly, an important object of the present invention to provide an improved cleaner drive assembly for driving a cleaner unit for an endless wire-screen or felt-blanket belt used in the sheet forming station of a papermaking apparatus.
It is another important object of the present invention to provide a cleaner drive assembly which will guarantee the designed service life of the wire-screen or felt-blanket belt to be cleaned by a belt cleaner.
It is still another important object of the present invention to provide a cleaner drive assembly which will enable a belt cleaner for a wire-screen or felt-blanket belt to clean the belt uniformly throughout the external surface thereof.
It is still another important object of the present invention to provide a cleaner drive assembly which is capable driving a belt cleaner without repeated interruptions of the reciprocating motions of the cleaner at the opposite ends of each stroke of the cleaner.
It is still another important object of the present invention to provide a cleaner drive assembly which will enable a belt cleaner to operate at a higher speed competent with the increased production speed of a modernized papermaking apparatus.
It is, yet, still another important object of the present invention to provide an improved cleaner drive assembly adapted to drive the water distribution pipe of a shower pipe unit to clean a wire-screen or felt-blanket belt provided in the sheet forming station of a papermaking apparatus.